Cab Share: What are the current barriers preventing people from sharing taxis?

My idea is to develope a means to share cab rides that not only save money for the customers but also provides increased revenues for drivers. What would be the environmental benefits? And do these benefits outweigh the current barriers? How could you make this idea financially viable?

Apr 16 2012:
Time Issues.
As time is important for every person,if people need to share cab then cab need to pick up at there specific point and drop out people at there preferred destinations and it may consume some time and traffic is one more issue.so time optimization is rally important and it can be best done by people sharing a cab if they have the same preferred destinations and nearby pickup locations.

Apr 17 2012:
I agree with you Hans, that safety is a big issue. Maybe if you would create kind of a community where people have to sign up first. That could provide a certain safety improvement. Otherwise I don't really know how to improve safety, do you?
Most of the taxis are equiped with cameras which would provide a certain base safety for the driver, but also for the customers.

Apr 16 2012:
Very interesting concept Lu Lu, I had thoughts about this too. I guess one of the major barrier would be the security issues and how you could overcome these. Maybe by creating some sort of service where you have to sign up in order to be able to use it.

Apr 16 2012:
To make it financially viable, maybe you can charge the people who wanted to use the application per rides? and maybe you can link the app with the taxi's company gps system so that people will be alerted which taxi is the closest to them as well?